This invention relates to a part fixing method for fixing a part on a main base and, more particularly, to a part fixing method for fixing, on an optical base for use in an optical pickup, a part such as a leaf spring or a photodiode (PD) base to which a photodiode is adhered.
In the manner known in the art, an electric equipment such as a personal computer is connected to various peripheral units one of which comprises a memory device or a recording medium. In addition, there are various types of memory devices (recording media). In other words, the memory devices (recording media) are classified into removable media and non-removable media. On of the removable media comprises a compact disc recordable (CD-R). The compact disc recordable is an addible recording medium which is compatible with a compact disc read only memory (CR-ROM) or a compact disc-digital audio (CD-DA). Although to write information (data) in the CD-R requires an exclusive apparatus or a CD-R drive and a writing application, to read the information (data) from the CD-R may be carried out by using a CD-ROM drive. Although it is impossible to cancel the date once written, it is possible to frequently add data.
Various other removable media are already known. A compact disc-rewritable (CD-RW) is a compact disc which is capable of erasing data therefrom and of rewriting data therein many times.
Now, in order to write information (data) in the CD-R or the CD-RN and to read the information (data) from the CD-R or the CD-RN demands a recording/reproducing optical pickup requires for irradiating a laser beam on the CD-R or the CD-RW.
In general, the optical pickup of the type described comprises a laser optical source for outputting the laser beam and an optical system for guiding the outputted laser beam to a recording medium such as an optical disc. As described above, it is possible for the CD-R and the CD-RW to carry out not only reading of information but also writing of information. In the optical pickup for the CD-R and the CD-RW, it is necessary to change output or power of the laser beam outputted by the laser optical source either on reading of information or on writing of information. This is because writing of information is carried out by forming a pit in a recording layer of the optical disc by irradiating of the laser beam. Accordingly, the output of the laser beam on writing of information is larger than that on reading of information and is, for example, ten to twenty times as large as that on reading of information.
In the manner which will later be described in conjunction with FIGS. 4A. 4B, 5A, and 5B, the optical pickup comprises an optical base on which various parts are mounted and mechanically fixed. Among the parts, a metallic leaf spring or a metallic PD base to which a photodiode is adhered is mechanically fixed on the optical base by using one or more screws in prior art.
However, a conventional fixing method using the screw(s) involves problems in the manner which will presently be described. Firstly, it is difficult to cost down because of use of the screws. Secondly, a fastening torque control required to screw fastening is carried out. Thirdly, location slip on fixing may easily occur at a place required for precise positioning where the screws and ultraviolet (UV) curing resin are used together such as the PD base. This is because friction torque occurs due to fastening of the screw(s). Fourthly, it is difficult in the fixing method using the screw(s) to try positioning and fixing again in a case where the UV curing resin stiffens with presence of the location slip and it results in taking much time. Fifthly, it is difficult in a case of fixing the PD base on the optical base to easily carry out exchange of parts although only the photodiode is broken down.